The present invention relates to multi-layered containers. More particularly, the present invention relates to blow molded multi-layer plastic containers having a carbon-treated internal surface and a method for making such containers.
Multi-layer plastic containers are commonly used for packaging items in a wide range of fields, including food and beverage, medicine, health and beauty, and home products. Plastic containers are known for being easily molded, cost competitive, lightweight, and generally suitable for many applications. Multi-layered containers provide the added benefit of being able to use different materials in each of the layers, wherein each material has a specific property adapted to perform a desired function.
Because plastic containers may permit low molecular gases, such as oxygen and carbon dioxide, to slowly permeate through their physical configurations, the use of plastic containers sometimes proves to be less desirable when compared to containers formed from other less permeable materials, such as metal or glass. In most applications, the shelf life of the product contents is directly related to the package""s ability to effectively address such molecular permeation. In the case of carbonated beverages, such as beer, oxygen in the atmosphere surrounding the container can gradually permeate inwardly through the plastic walls of the container to reach inside of the container and deteriorate the contents. Likewise, carbon dioxide gas associated with the contents may permeate outwardly through the plastic walls of the container until eventually being released on the outside, causing the carbonated beverage to lose some of its savor and possibly become xe2x80x9cflat.xe2x80x9d
To address some to the foregoing concerns, plastic container manufacturers have utilized various techniques to reduce or eliminate the absorption and/or permeability of such gases. Some of the more common techniques include: increasing the thickness of all or portions of the walls of the container; incorporating one or more barrier layers into the wall structure; including oxygen-scavenging or reacting materials within the walls of the container; and applying various coatings to the internal and/or external surface of the container. However, a number of conventional barrier and/or scavenger materials will not effectively curtail the permeation of both oxygen and carbon dioxide over extended periods of time. Moreover, there are usually other practical concerns associated with most conventional techniques, most commonly, increased material costs and/or production inefficiencies.
In recent times, the use of plastics has become a significant social issue. Recycling has become an increasingly important environmental concern and a number of governments and regulatory authorities continue to address the matter. In a number of jurisdictions, legislation pertaining to minimum recycled plastic content and the collection, return, and reuse of plastic containers has either been considered or has already been enacted. For example, in the case of plastic containers used to hold consumable items, such as food items or beverages, regulations often require a certain content and minimum thickness of the innermost layer that comes in contact with the contents. Conventional processes, such as co- or multiple-injection molding, are often limited as to the amount of recycled plastic that can be effectively incorporated into the structure of the container. Commonly, the amount of recycled content that can be effectively incorporated into conventional co-injection molded containers that are suitable for food contents is less than 40% of the total weight of the container.
Therefore, a need exists in the industry for an improved multi-layered plastic container having a high recycled content that is suitable for holding carbonated products, such as carbonated beverages, and provides an acceptable level of performance when compared to commercial containers formed from alternative materials. A further need exists for a method to produce such containers in high volume commercial rates using conventional equipment.
Recognizing the problems and concerns associated with conventional multi-layered plastic containers, especially those used to hold carbonated beverages, a multi-layer plastic container having enhanced gas barrier properties and a high content of recycled plastic is provided. A container constructed in accordance with the principles of the present invention provides several advantages over those previously available. Such advantages are generally realized through the use of a both a carbon coating on the internal surface of an inner layer, wherein the inner layer may have a controllably-varied thickness and a significant amount of outer recycled content. Furthermore, the improved container can be produced using conventional processing techniques and manufacturing equipment.
An important aspect of the present invention is its ability to incorporate the functional benefits of an exceptionally thin, but very effective, barrier with the functional and commercial benefits associated with having an outer layer comprised a significant amount of recycled plastic content. Further, the ease in subsequently recycling a container produced in accordance with the principles of the present invention make the practice of the invention extremely advantageous. Moreover, the present invention provides the additional advantage of permitting the manufacturer to controllably vary the material positioning and wall thickness at any given location along the vertical length of the inner and/or outer layers of the container.
In accordance with the principles of the present invention, a blow molded multi-layer container is provided having an upper wall portion, an intermediate sidewall portion positioned beneath the upper wall portion, and a base portion positioned beneath the intermediate sidewall portion, the base portion being adapted to dependently or independently support the container. The container includes (i) a molded inner layer formed from a plastic material, the inner layer having a vertical length and a carbon-treated inner surface; and (ii) a molded outer layer formed from recycled plastic that is substantially coextensive with the inner layer. The recycled outer layer comprises at least 40% by weight of the overall weight of the container, but can comprise more than 90% by weight, depending upon the needs of the application. In a preferred embodiment, the thickness of the inner and/or outer layers is controllably adjusted along their respective vertical lengths. If functionally desirable, the inner layer and/or outer layer may also include additional barrier materials and/or oxygen scavenging/reacting materials.
Other and further advantages and novel features of the invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings, wherein, by way of illustration and example, embodiments of the present invention are disclosed.